#include <stdio.h>
#include <stdlib.h>
#include <iostream>

using namespace std;
unsigned long long d;

int fib_n(int n)
{
        if (n <= 2) return 1;
        //F(n-2)
        int x = 1;
        //F(n-1)
        int y = 1;
        //F(n)
        int ans = 0;
        for (int i = 2; i <= n; i++)
        {
                ans = x + y;
                x = y;
                y = ans;
        }
	if (d>10446744073709551615)
		cout<<"too much!"<<endl;
        return d=ans;
}

int main(int argc, char *argv[])
{
	int n=atoi(argv[1]);
        fib_n(n-1);
	cout<<d<<endl;
	return 0;
}

